The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art.
Transmissions, particularly hydraulically controlled planetary gear automatic transmissions for motor vehicles, operate at temperatures well above ambient, often at 130° C. (265° F.) or higher. Because they may begin operation at ambient temperature as low as −35° C. (−30° F.) or lower, the air within the transmission will undergo significant expansion. Conversely, when they become inactive, their nominal temperature may drop relatively rapidly and the air within the transmission will contract. In order to accommodate these changes and to avoid pressurization or a partial vacuum within the transmission, they are equipped with a breather system which allows exhaust and ingestion of air.
When the transmission temperature is rising and air is being driven out of the transmission through the breather system, the only likely operational difficulty is the blocking or plugging of the breather system which would result in pressurization of the transmission. Conversely, a temperature drop is accompanied by ingestion of air through the breather system. This can have adverse consequences if water becomes entrained with the entering air. While this might appear to be an uncommon occurrence, a sudden temperature drop may be caused by the immersion of the transmission in water as a vehicle operator attempts to navigate a flooded roadway or stream. At the same time, a large quantity of water may come in contact with or essentially surround the breather system inlet/outlet and be drawn in with the ingested air, resulting in water in the transmission.
This is highly undesirable and the present invention is directed to reducing or eliminating the ingestion of water into a transmission through the breather system.